Nonsense.
To better understand what constitutes PC for police to enter a private residence without permission of the owner or resident, it's helpful if you will to imagine the cop(s) having a judge in their car to whom they could right on the spot apply for a warrant to legally enter.
Now Gates's allowing the police officer to enter without protest essentially waived his 4th Amendment protections against police entry...but the scenario you're supposing is that police needed nothing more than a complaintant saying they saw someone trying to force the door.
With that information solely, this is pretty much how a warrant application would be handled:
PoliceOfficer: We have a report from a passerby that she saw two men attempting to force the front door open. We went to the closed front door where we could see two men through the glass.
Judge: Were either of the men a resident clearly involved in burglarizing the home?
P: No.
J: Did you identify either of the men.
P: One man told us his name Henry Gates - and that he was the resident.
J: Did he give you permission to enter?
And this is where the actual events of the case veer from what could have otherwise happened had Gates denied the officers entry.
Had he denied them entry:
P: No, he would not give us permission to enter
J: Did you verify if Mr Gates was the legal resident?
P: No
J: Was either man visibly commiting a crime in your view?
P: No
And that's that. What then are the legal options for the officer(s) if they still feel that the men inside may NOT be the legal resident(s)?
First, they can continue observing the house to assure the men inside do not begin acting in a suspected criminal manner (removing valuables from the home and placing them in a vehicle etc).
While doing that, they can with reasonable ease identify the actual owner of the home, likely within a few minutes.
They can knock on neighboring doors and ask other residents if they know who the resident is at the cited residence.
They can of course also ask passersby if they are aware of the identity of the true resident of the cited residence.
In the specific case, they could even ask any of the above people to take a look through the glass windows (as the cops themselves had already done) and tell the cops if they recognize the men inside as one or more of the legal residents of the cited house.
There are likely several other reasonable and legal methods the cops may employ to better determine if the men inside are there without permission of the legal owner or resident.
But one method they absolutely CANNOT do is enter the residence without permission of the owner or legal resident UNLESS they have clear and persuasive evidence that the men inside are committing a crime.
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That's useful information for any of us who might receive a knock on the door from police for any reason. Gates correctly followed the law when he identified himself to Crowley.
Since he was not operating a vehicle, nor was a non-citizen immigrant, he is not required by law to show any kind of identification, though that does not preclude the officer asking for such.
However, he did offer to procure identification, which is his free choice.
Where he messed up is that he did not then close the door in the officer's face or tell the officer, "Wait here please and do not come in my house".
And then, as most all of us agree, he erred even further by then initiating a verbal smakdown on the officer.
Though fully legal, that placed the officer in a difficult position from a point of pride. While he (Crowley) should have simply turned and left the house, he instead decided to arrest Gates. And though the charge was without merit, there was nothing that Gates could then do save to forcibly resist that arrest - itself a separate and distinct crime.
